Two others were taken to Christiana Hospital by ambulance.
Russ Kilmer of the Avondale Fire Company said the victims had second-degree burns over "considerable" amounts of their bodies.
Flames broke out shortly before 10:00 a.m. in the 1400 block of Baltimore Pike in New Garden Township.
Firefighters wasted no time snuffing out the flames in the two story stone faced home that appears to have a family-run business in the back.
Three to four fire fighters suffered from heat exhaustion but did not need to be taken to hospitals for treatment.
It took them 30 to 40 minutes to extinguish the flames.
The fire went to two alarms.
Investigators have no indication yet as to what touched off the fire.
However, unconfirmed reports indicate the father and teenager may have been arguing before the fire. That is believed to be part of the investigation.
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